Split-phase system.



E. F; W. ALEXANDERSON.

SPLIT PHAS'E SYSTEM. APPLICA'HON FILED IAN-29, 1914. RENEWED JULY 20, 1915.

1,170,21 1. Patnted Feb. 1, 1.956.

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E. F. W. ALEXANDERSONL SPLIT PHASE SY STEM. APPLICATION FILED JAN. 29,1914. RENEWED JULY 20, I915- 1,170,21 1. Patented Feb., 1, 1916.

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WZ'TZVESSEE' fxz YEN TUH y y ERNST Z'T' WY ELEXANDERSOA;

w a WQ His ATTURNEII I Application filed January 29, 1914, Serial No. 815,279. Renewed July 20, 1915.

I frequently the transformer secondary aratus is grounded. It then becomes safely increase the working UNITED A STATES PATENT orrrcn.

nnns'r F. w. annxa'nnnason, or scnnnncranr, NEW YORK, ASSIGNOR TO GENERAL COMPANY, A CORPORATION OF NEW YORK.

SPLIT-PHASE sYs'rEM.

To all whom it may concern: a

Be it known that I, ERNST F. W.- ALEX- i'NnnnsoN, a; citizen of the United States, residing at Sc-.enectady, in the county 0 Schenectady, jState of New York, have invented certain new and useful Improve; ments in Split-Phase Systems, of which the following is a specification.

-My invention relates rent polyphas'e motors, larly to the use of such motors in a so-called split phase system with a single phase source of supply and av phase converter and'especially in a split phase system of the type described in my Patent No. 1,150,652. \Vhen polyphase motors are supplied with energy from a single phase source of supply with the use of a phase converter, it is desirable touse a number ofmotorswith a single phase converter. n order, then, that the current carrying capacityof the apparatus used shall not exceed its normal limit, it .is necessary to increase the working potential. Such an artifice may, however, cause such an insulation strain on the windings that it will be as prohibitive an arrangement as would an in-. creased current. Frequently, as in locomotive practice, a transformer is interposed between the supply-and the apparatus. may'then be that one of the windings of or of the'other PP necessary to limit the potential to ground from any point in the windings.

If there is no ground connection, then it is just as necessary to limit the static strain on the apparatus- To meet these conditions and overcome the difii'culties encountered, I have accordingly devised a novel arrangement 0 the elements involved,and the object of my invention is 'tof's ov arrange the secondary windings of a supply transformer and the windings of a phase converter and polyphase motors conne' ted thereto that I may potential without substantially increasing the insulation strain on the apparatus. Ido this by providing a plurality of secondary transformer windings and so connecting these (in such a sequence) with the related motor and converter phases that the potential strain on the insulation of the windings iswithin' normal limitsi'f v I My .inven ion will be more readlly': alflder;

Specification of Letterslatent.

to alternating cur and more particle It prises a i be seen that the outer termma' a y enable" a. variable Patented Feb. 1. 1916.

Serial, No. 41,014.

stood when taken in connection with the following description and the accompanying drawings,'in which- Y Figures 1, 2 and 3 are diagrams showing various arrangements for connecting the es-. sential elements according to my invention. InFig. 1, one of the secondary windings of thetransformer is provided with a ground, and the control is effected by simultaneously varying the impressed voltage on one phase of motor and converter and the interpolated voltage on the other phase of motor and converter. In Fig. 2 a ground is provided on one phase of the motor windmg, and in this arrangement the impressed voltage is varied, but the interpolated voltage is kept constant. In Fig. 3, no ground is provided, but the motors are designed with a neutral point and the interpolated "oltage is supplied by a separate transformer secondary. The control is effected by varying the impressed voltage on one phase of the motor and converter. Figs. 4, 5 and 6 are vector diagrams illustrating the resulting conditions during running for the respective connections shown in Figs.

1, 2 and 3. v

In general, it will be seen that each of the arrangements shown in Figs. 1, 2 and 3 comtransformer connected to the source of supply, more motors which are connected in parallel. For the purposes of illustration in each case, I have shown the preferred form as comprising windings associated with a single primary winding, but it will be obvious to those skilled in the art that other equivalent constructions might equally well be substituted.

In Fig. 1, the primary P is connected to a single phase source of supply and in inductive relation to this primary winding are two secondary windings S, and S Connected between and in series with the two secondaries is phase ofthe converter, designated C.., or' free terminals of the secondaries is phase A of the motor, designatedas M... ,It' will 1 tot S indicated as a movable contact, and it beunderstood that-the transformer secon will 'be provided. with suitable taps to volta to efr s on phase'fA of the motor and eonverter.

the .ispbification and-the .q -i 'lms, when a plurality of secondary a phase converter, and one or while connected to the outer speak of the free terminals of the secondary windings; I intend merely to designate any terminals or taps to which C is not con nected, and do not refer merely to the extreme ends of the secondary windings.

Phase B of motor and-converter, compris ing M and C are connected in series, and

one terminal of M is connected to the fixed point '2 on 8,, while the free terminal of C5 is connected to the movable contact 1. For the purposes of control connect ons for elements not shown in the drawing, I find itconvenient to supply a ground connection at some point 8, preferably the middle point.

voltages in the various windings. their rela-,.

tive lengths indicating the relative values of these voltages and the angles between them representing the phase relations. Besidethis, each of the lines in the vector diagram may be taken 'to' represent the correspondimg winding. It will then be seen that the d1agram correctly represents the "actual connections, the free terminal of M being connected to thepoint 2 on S and the joint terminal of "M. and C being-connected at 1. Inasmuch as the vector diagram is drawn to represent the conditions obtained in the running position of the control, the point 1 has been moved to the extreme end of S At- 3 is indicated the ground connection which is preferably ,at the middle point of 8,. It then results, as will be apparent from an inspection of the drawing, that the points "of extreme potential to ground are indicated by the numerals .1, 10, 11, 12' and 13:, and all these will be substantially equal distances from the ground connection, Inasmuch as the linear distance between any point on the vector diagram and the paint. 3 represents the potential to ground ofthe corresponding point of the various windings, it will be seen that the voltage strains are evenly distributed and are in no instance excessive. This relation results from the particular sequence of connections between the various windings, which constitutes the essence of my invention. i

In Fig. 2, the primary P has associated therewith secondariesS and S Phase C of the converter, designated C is connected between S and 8,, while phase C of the motor is connected to the free terminals of S, and 8,, one of these (the'terminal 4:) being a movable connection, as in Fig. 1. In this arrangement a ground connection is provided at 6, substantially the middle point pf phase D of the motors. C and M are .double that of the voltage strain.

conn'ected in series between the point 5 on-k S5, which is preferably substantially the middle point thereof, while the other terminal isconnected to the outer end of S The corresponding vector diagram'shown in Fig. 5 represents the conditions obtalned when running, and the correspondingly lettered cates the condition-s obtained when running,

the point 4'has been moved to theextreme end-of S in order to impress the maximum potential on phase C of motor'and converter. Itwill be seen that the interpolated voltage on phase D is here kept constant,

"while the impressed voltage, on phase C is varied;

In Fig. 3, the primary P has associated therewith secondary windings S S and 8,. Between the secondaries S, and S C representing phase E of the converter, is connected, while phase E of the motor, designated as M is connected between -theouter terminal S and the movable contact 7. Phase F of motor and converter is connected in series and the interpolated voltage is sup-' plied from the secondary S,. In this in-- stance a neutral connection at 8 'is provided between the two motor phases.

The corresponding vector diagram, Fig.

6, shows that a similar condition here re sults as in the previous arrangement, and

that the points of extreme potential, as at -7' and 20 to 25, inclusive, are substantially equidistant from the neutral point 8. Here, 7

again, the diagram represents conditions when running, and the movable contact 7 is shown as connected atthe extreme end of S It will, therefore, be seen that by means of the particular sequence of windings which isembodied in each of the arrangements shown in Figs. 1, 2 and 3, I am enabled to keep the potential strain on the windings" within normal limits and at the sametime provide a working potential substantially I have, therefore, succeeded in carrying out the'object of my invention as previously specified.

:'and amable to use twice the number of motors without increasing the current to be handled by the control systemor any one element, and,further, without increasing the. potential strain on the windings of the various pieces of apparatus. Such an arrangement is of great practical importance because it enables the construction of a source of motive power, such, for instance, as might be used upon an electric locomotive, of very high power, without exceeding the current capacity of the motors .and of the contactors of ordinary design, and withed claims all such variations which fall within the true scope and spirit of my invention.

of my invention, and I therefore seek to cover in the append- What I claim as new and desire to secure by Letters Patent of the United States, is

1. In combination, a phase converter, a motor, and a plurality of secondary transformer windings,-a phase of said converter anda phase of said motor being connected between two of the secondary transformer windings so that said secondary windings are interposed between the terminals of the machine windings, another phase of said converter being connected to another phase of said motor and to a secondary transformer winding.

2. In combination, a phase converter, a

quarter-phase motor, and a plurality of secondary transformer windings, one phase of said converter being connected in series with two of said secondary transformer windings andwith one phase of said motor so that said secondary windings alternate with said machine windings, another phase of said converter being connected in series with another phase of said motor and witl" a secondary transformer winding having an induced voltage different from the maximum voltageimpressed on said first-mentioned phases. I

3. In combination, a single phase source of supply, a phase converter, 'a quarterphase motor, and a transformer with its primary connected to said supply and its secondary divided into sections, one phase of said converter minal of each of two of the sections of the secondary, one phase of said motor being connected to the free terminals of said sections, another phase of said converter being connected in serieswith another phase of said motor, and means. foi"interpolating a voltage different from that of said source in the latter circuit.

In witness whereof, I have hereunto set my hand this 28th day of January, 1914:.

-ERNS T F. w. ALEXANDER-SON.

Witnesses:

BENJAMIN B. HULL, MARGARET E. IVooLLnY.

being' connected to one ter- 

